Studies have shown that most people value their personal space, find physical proximity to be psychologically and in some cases physically disturbing and uncomfortable, and feel discomfort, anger, anxiety and other effects when their personal space is encroached or they are over stimulated because of crowded conditions. In addition, studies have shown that heart rate, blood pressure, and skin conductance increase when people are in crowded spaces or spaces that they anticipate will become crowded where they have little or no control over maintaining their personal space and level of stimulation. Public places are often crowded and are becoming more so. In public places where seating is available, individual seating spaces are often not demarcated or are demarcated but not physically divided. Often people will encroach into what is intended to be the space of the person seated next to them. Theatres, sporting events, institutions of formal education and testing, and governmental service locations are a few of the many examples of public places with crowded seating conditions.
Public transportation vehicles are also examples of public spaces that are often crowded, with crowded seating conditions. Subways, cars, airplanes, trains, buses, and other modes of public transportation often allow little space for each individual. For example, in many subway cars, the seats are of a bench style. Though each individual space is often marked in some manner, often no armrests, dividers, or barriers exist between individual seating spaces, or if they do, they are often inadequate to ensure that each person remains within one space and does not encroach physically, or in some other manner, on the space of the person beside them. One seated passenger may eat, engage in personal grooming, cough, sneeze, physically rub against, stare, and otherwise provide unwanted stimuli to the person beside whom they are seated. There have even been cases of passengers urinating on bench seats with the urine running onto the seat and person seated next to them and of passengers vomiting and bleeding on passengers seated beside them.
People with disorders or conditions (or both) that compromise the brain's ability to process and integrate certain information received from the body's five basic sensory systems can be especially impacted by having to sit in close proximity to others, in crowded situations, or both. Such sensory processing and integrative problems, comprising but not limited to learning disabilities, autism spectrum disorders, stress-related disorders, anxiety disorders, attention-deficit hyperactivity disorder, post-traumatic stress disorder, and brain injury are found in many children and adults. In some cases, people with at least one of these conditions or disorders are not capable of being in situations where the person is likely or certain to be in the conditions described above. This can mean that these people are unable to conduct certain activities, for example use public transportation. Because some of these people are also unable to drive or cannot afford to own a vehicle of their own, this lack of ability to have control over the proximity or stimulation in the crowded seating situation renders them without affordable, reliable transportation, greatly limiting their access to education, employment, and other societal necessities. Even people without these disorders and conditions may be sensitive to stimulation created by people in close physical proximity, even though some are not consciously aware of the effects.